The Collaboration Univ. of California-Davis, CBPF-Rio de Janeiro, CINVESTAV-Mexico City, Univ. Colorado-Boulder, FERMILAB, Laboratori Nazionali di Frascati,

CHARM MIXING CHARM MIXING AND CP VIOLATION AND CP VIOLATION

IN FOCUS IN FOCUS AT FERMILABAT FERMILAB

CHARM MIXING CHARM MIXING AND CP VIOLATION AND CP VIOLATION

IN FOCUS IN FOCUS AT FERMILABAT FERMILAB

EPS-HEP2001Budapest, , july 12-18, 2001EPS-HEP2001

Budapest, , july 12-18, 2001

SERGIO P. RATTISERGIO P. RATTIINFN and Dipartimento di Fisica Nucleare e Teorica - PAVIA

for the FOCUS COLLABORATIONfor the FOCUS COLLABORATION

Outline of the talkBasic phenomenolgy: Do-Do mixing:lifetime mixing: yCP=DCS decay Do K+- (from D*)Comparison with other experimentsD-D asymmetries: search for CPConclusions

2

yxR

22

unmixed

mixmix

INTEGRATING |AINTEGRATING |Amixmix||22 OVER TIME, MIXING IS DESCRIBED BY: OVER TIME, MIXING IS DESCRIBED BY:INTEGRATING |AINTEGRATING |Amixmix||22 OVER TIME, MIXING IS DESCRIBED BY: OVER TIME, MIXING IS DESCRIBED BY:

Do-Do MIXINGDo-Do MIXING

)]cos(21[)( 2/)(2

00 1 mteeetDD ttt )]cos(21[)( 2/)(

200 1 mteeetDD ttt

THE MIXING AMPLITUDE SQUARE IS:THE MIXING AMPLITUDE SQUARE IS:

2

yxR

22

unmixed

mixmix

2

yxR

22

unmixed

mixmix

For a HADRONIC DECAY Do K+- For a HADRONIC DECAY Do K+-

RRWSWS=(Do K+- )/(Do K-+ )ee--tt[R[RDCSDCS+R’/2 t+R’/2 t22 +y’ t +y’ t RRDCSDCS]

RRWSWS=(Do K+- )/(Do K-+ )ee--tt[R[RDCSDCS+R’/2 t+R’/2 t22 +y’ t +y’ t RRDCSDCS]

Do K-+ is C.F.Do K+- is WRONG SIGNWRONG SIGN

D.C.SD.C.S. orfrom mixing box diagrammixing box diagram

Do K-+ is C.F.Do K+- is WRONG SIGNWRONG SIGN

D.C.SD.C.S. orfrom mixing box diagrammixing box diagram

STRONG PHASE STRONG PHASE y’= y cos x sin

x’= x cos y sinR’=(x’2+y’2)/2

STRONG PHASE STRONG PHASE y’= y cos x sin

x’= x cos y sinR’=(x’2+y’2)/2

KDD 00

KD0

0* DD

c

u ud

u

sK

cdVusV

0D

DCSDCS

0D Ku

s

s

u

c sd

u

c

csV

udV

BOXBOX

or

Do-Do lifetime mixing

Do-Do lifetime mixing

LIFETIME MIXINGLIFETIME MIXING

and 2

)]([;)]([ 0 KDKKD o

and 2

)]([;)]([ 0 KDKKD o

assuming CP conserved :assuming CP conserved :

CP|k+k->=+1; CP |k-+>=equal mixture. Therefore:

Thus:

1)]([

)]([y CP

KK

Ko

o

D

D

Mkk

Mkk

Mkk

Mkk

SAMPLE HANDLINGSAMPLE HANDLING

Do KKis CP=+1Do KKis CP=+1

need over10,000 ev.to reach

1% errorin

need over10,000 ev.to reach

1% errorin

Fit spanning Fit spanning overover

~10 ~10 !!!!

Fit spanning Fit spanning overover

~10 ~10 !!!!

Fitting Fitting (D(Doo[K[K]) and y]) and ycpcpFitting Fitting (D(Doo[K[K]) and y]) and ycpcp

10,331 events

119,738 events

MEASUREMENTS MEASUREMENTS

ResultsResults

Mass (GeV)

Phys. Lett. B485, 62 (2000)Phys. Lett. B485, 62 (2000)Phys. Lett. B485, 62 (2000)Phys. Lett. B485, 62 (2000)

yCP= 3.42 1.39 0.74 %yCP= 3.42 1.39 0.74 %

=409.40 1.34 ?? fs=409.40 1.34 ?? fs

SPECULATIONSSPECULATIONS

(KK)= =(395.8±5.5) fs(KK)= =(395.8±5.5) fs 2= (415.5 ± 11.5) fs 2= (415.5 ± 11.5) fs

Purely speculative: nsPurely speculative: ns

Just for the fun of it!!! From: 2 1

(K) = and yCP get (KK)= ; 1

+ 2 1

1 - 2

ycp= get -=1/ 2 ; get .

1 + 2

From:

1

E791 0.82.91 %

(CLEO mixing) ( 5.8<y<1 %)

FOCUS 3.421.390.74 %

BELLE prel. 1.671.651.16

%

CLEO prel -1.12.51.4 %

1.81.0 %Average yCP 2 = 2.3 for 3

Conclusion: BELLE, CLEO, E791 and FOCUS

The comparison to CLEO mixing analysis isvaild only if one assumes a small strongphase difference .

95% CL

FOCUS

CLEO

E791

BELLE

CLEO

E791

x

y

Comparison of yCP measurementsComparison of yCP measurements

semileptonic

DoK+-

from D*DoK+-

from D*

The CLUE of the WRONG SIGN STUDIESWRONG SIGN STUDIES when the nature of the Do meson is identified by the parent D*

is the RESPONSE OF THE CERENKOV COUNTERS to solve the K K AMBIGUITY AMBIGUITY

MORE SO since we have to directly compare KK-- ++ to K to K++ --

single misidentification implies “regular background”DOUBLE MISIDENTIFICATION WOULD RETAIN THE DOUBLE MISIDENTIFICATION WOULD RETAIN THE

EVENT EVENT BUT BUT IN THE WRONG CATEGORY!!!!IN THE WRONG CATEGORY!!!!

The CLUE of the WRONG SIGN STUDIESWRONG SIGN STUDIES when the nature of the Do meson is identified by the parent D*

is the RESPONSE OF THE CERENKOV COUNTERS to solve the K K AMBIGUITY AMBIGUITY

MORE SO since we have to directly compare KK-- ++ to K to K++ --

single misidentification implies “regular background”DOUBLE MISIDENTIFICATION WOULD RETAIN THE DOUBLE MISIDENTIFICATION WOULD RETAIN THE

EVENT EVENT BUT BUT IN THE WRONG CATEGORY!!!!IN THE WRONG CATEGORY!!!!

STARTING FROM OVER 200,000 D* EVENTS,this study required a sistematic Montecarlo

investigation to sort out the wrong sign K+- signal (either DCS decay or BOX diagram decay)

from the overwelming background.

STARTING FROM OVER 200,000 D* EVENTS,this study required a sistematic Montecarlo

investigation to sort out the wrong sign K+- signal (either DCS decay or BOX diagram decay)

from the overwelming background.

Simulate 3 different types of background, i.e.:Do+-; DoK+K-; partially reconstructed D’sand DoK double misidentified; double misid.Do‘shandled with adequate Cerenkov cuts. Subdivide the M distribution into 1 MeV bins and fit the remaining backgrounds plus signal to M(K).

Simulate 3 different types of background, i.e.:Do+-; DoK+K-; partially reconstructed D’sand DoK double misidentified; double misid.Do‘shandled with adequate Cerenkov cuts. Subdivide the M distribution into 1 MeV bins and fit the remaining backgrounds plus signal to M(K).

When the wrong K havemass around the right K!M=MD*-MD is at the peak!

When the wrong K havemass around the right K!M=MD*-MD is at the peak!

Make a total of 80 fits (wrong sign and right sign) on 40 1 MeV strips

Make a total of 80 fits (wrong sign and right sign) on 40 1 MeV strips

Y=36760 ± 195 Y=148.5 ± 31.3

M

We obtain: RWS=(0.405 ± 0.085 ± 0.025)%Of course -as we have seen- RWS becomes

a function of t in presence of mixing

We obtain: RWS=(0.405 ± 0.085 ± 0.025)%Of course -as we have seen- RWS becomes

a function of t in presence of mixing

Consistent with SM Cabibbo tg4Consistent with SM Cabibbo tg4

Phys. Rev. Lett. Phys. Rev. Lett. 8686,2955,2001,2955,2001

19

34

21

45

0.77 ± 0.25 ± 0.25

0.68 ± 0.07

1.77 ± 0.31

0.332 ± 0.040

CLEOCLEO

E791E791

ALEPHALEPH

CLEO II.VCLEO II.V

EventsEventsRRDCSCDCSC(%)(%)

+0.34-0.33

+0.063-0.065

+0.60-0.56

with mixing assumption and

22'2'

' /4

/ tyx

tyRRR DCSDDCSDWS

t/=1.578±.008(t/=3.61±.03estimate t/ and (t/ using MC

Rws=(0.404 ±.085 ±.025

CP asymmetries

CP asymmetries

CP asymmetry for D mesonsCP asymmetry for D mesonsCP asymmetry for D mesonsCP asymmetry for D mesons

1623±47

18501±144

1706±53

19633±149

6860±110 7355±112

73710±29268607±282

Parameter A for D mesonsParameter A for D mesonsParameter A for D mesonsParameter A for D mesons

Comparison to other experimentss

No evidence for CP violation so far. Our limit on No evidence for CP violation so far. Our limit on KK++KK- - needs tagged Dneeds tagged Doo ‘s from D ‘s from D**, which cuts our , which cuts our

sample bysample by ~80%.~80%.

Our limits: most precise published Our limits: most precise published measurements reflecting our large statistics.measurements reflecting our large statistics.

ConclusionsConclusionsConclusionsConclusions

can we speculate that Do-Do mixing is 0?yCP=(3.42±1.39±0.74)% has a 90% CL limit 0.

Rws=(0.404 ±.085 ±.025)% would beRDCSD in absence of mixing

if mixing Rws compatible with CLEO IINo evidence for CP violation at 1% level semileptonic decays still to be tackled

CP=-1 states still to be adressed

can we speculate that Do-Do mixing is 0?yCP=(3.42±1.39±0.74)% has a 90% CL limit 0.

Rws=(0.404 ±.085 ±.025)% would beRDCSD in absence of mixing

if mixing Rws compatible with CLEO IINo evidence for CP violation at 1% level semileptonic decays still to be tackled

CP=-1 states still to be adressed